PROJECT SUMMARY: The ideal response to tissue injury is regeneration, with the complete restoration of normal tissue architecture. Unfortunately, mature skin generally heals through a repair process which results in the formation of scar tissue instead of normal tissue. In addition to the cosmetic concerns associated with scars, scar tissue is weaker than normal skin and is functionally defective. Interestingly, at early stages of embryonic development, fetal skin is able to heal without a scar. We use a mouse model of fetal wound healing to compare regenerative, scarless wounds generated at embryonic day 15 (E15) and fibrotic, scar-forming wounds generated at embryonic day 18 (E18). Our lab has recently completed preliminary studies demonstrating that the glycoprotein Fetuin-A (FetA) is present at significantly higher levels in E18 fibroblasts, E18 skin, and E18 wounds compared to their E15 counterparts. Preliminary data also suggest that introduction of FetA into E15 fetal wounds disrupts the scarless healing process. The studies proposed here will test the ability of FetA to stimulate fibroblasts and promote scar formation. Because FetA has been shown to bind to and activate TLR4 in adipocytes and other TLR4 agonists have been shown to stimulate fibroblasts, we will also explore TLR4 activation as a potential mechanism by which FetA stimulates fibroblast activation and scar tissue production. The central hypothesis of the proposed studies is that FetA stimulates the production of scar tissue by fibroblasts in a TLR4-dependent manner. The following specific aims are proposed to test the hypothesis: Aim 1 ? Examine the effects of FetA on cultured dermal fibroblasts; Aim 2 ? Determine whether FetA promotes scar formation in vivo. This application is based on novel data generated by our lab suggesting that FetA is involved in scar formation. Very little is known about the function of FetA in the skin and the effects of FetA on fibroblasts/scar formation have not been examined. Therefore, this work is significant because it will provide important new scientific information. The studies have the potential to impact the field by establishing FetA-mediated TLR4 activation as a new mechanistic pathway involved in the formation of dysfunctional, debilitating scars.